Messages in this thread | | | Date | Thu, 21 Aug 2008 15:50:50 +0200 | From | Pierre Ossman <> | Subject | Re: [patch 2.6.27-rc3] at91_mci: don't use coherent dma buffers |
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Ok with you nicolas?
On Mon, 18 Aug 2008 16:07:21 -0700 David Brownell <david-b@pacbell.net> wrote:
> From: David Brownell <dbrownell@users.sourceforge.net> > > At91_mci is abusing dma_free_coherent(), which may not be called > with IRQs disabled. I saw "mkfs.ext3" on an MMC card objecting > voluminously as each write completed: > > WARNING: at arch/arm/mm/consistent.c:368 dma_free_coherent+0x2c/0x224() > [<c002726c>] (dump_stack+0x0/0x14) from [<c00387d4>] (warn_on_slowpath+0x4c/0x68) > [<c0038788>] (warn_on_slowpath+0x0/0x68) from [<c0028768>] (dma_free_coherent+0x2c/0x224) > r6:00008008 r5:ffc06000 r4:00000000 > [<c002873c>] (dma_free_coherent+0x0/0x224) from [<c01918ac>] (at91_mci_irq+0x374/0x420) > [<c0191538>] (at91_mci_irq+0x0/0x420) from [<c0065d9c>] (handle_IRQ_event+0x2c/0x6c) > ... > > This bug has been around for a LONG time. The MM warning is > from late 2005, but the driver merged a year later ... so I'm > puzzled why nobody noticed this before now. > > The fix involves noting that this buffer shouldn't be DMA-coherent; > it's just used for normal DMA writes. So replace it with standard > kmalloc() buffering and DMA mapping calls. > > This is the quickie fix. A better one would not rely on allocating > large bounce buffers. (Note that dma_alloc_coherent could have failed > too, but that case was ignored... kmalloc is a bit more likely to > fail though.) > > Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> > > --- > drivers/mmc/host/at91_mci.c | 20 ++++++++++++++++---- > 1 file changed, 16 insertions(+), 4 deletions(-) > > --- a/drivers/mmc/host/at91_mci.c > +++ b/drivers/mmc/host/at91_mci.c > @@ -621,12 +621,21 @@ static void at91_mci_send_command(struct > if (cpu_is_at91sam9260 () || cpu_is_at91sam9263()) > if (host->total_length < 12) > host->total_length = 12; > - host->buffer = dma_alloc_coherent(NULL, > - host->total_length, > - &host->physical_address, GFP_KERNEL); > + > + host->buffer = kmalloc(host->total_length, GFP_KERNEL); > + if (!host->buffer) { > + pr_debug("Can't alloc tx buffer\n"); > + cmd->error = -ENOMEM; > + mmc_request_done(host->mmc, host->request); > + return; > + } > > at91_mci_sg_to_dma(host, data); > > + host->physical_address = dma_map_single(NULL, > + host->buffer, host->total_length, > + DMA_TO_DEVICE); > + > pr_debug("Transmitting %d bytes\n", host->total_length); > > at91_mci_write(host, ATMEL_PDC_TPR, host->physical_address); > @@ -694,7 +703,10 @@ static void at91_mci_completed_command(s > cmd->resp[3] = at91_mci_read(host, AT91_MCI_RSPR(3)); > > if (host->buffer) { > - dma_free_coherent(NULL, host->total_length, host->buffer, host->physical_address); > + dma_unmap_single(NULL, > + host->physical_address, host->total_length, > + DMA_TO_DEVICE); > + kfree(host->buffer); > host->buffer = NULL; > } >
-- -- Pierre Ossman
Linux kernel, MMC maintainer http://www.kernel.org rdesktop, core developer http://www.rdesktop.org
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